Abstract
In a device for measuring a fill level of a liquid in a container with an ultrasonic sensor, wherein the ultrasonic sensor is arranged at the bottom end of a damping cup with a measuring tube, wherein the top area of the measuring tube has at least one inner ventilation hole and a cover assigned to the inner ventilation hole, which cover surrounds at least the upper end area of the measuring tube and itself has at least one outer ventilation hole, wherein at least one screen is present in the cover and is in contact with the cover at the top, it is provided that the screen which is in contact with the cover at the top extends horizontally from the measuring tube as far as a side wall of the cover. In addition at least four screens are provided between the one or more inner ventilation holes and the one or more outer ventilation holes, so that at least two air bubbles are trapped in the region of the screen when the device is in operation.
Claims
1. A Device for measuring a fill level of a liquid in a container having an ultrasonic sensor, wherein the ultrasonic sensor is arranged at the bottom end of a damping cup with a measuring tube, wherein the measuring tube has at least one inner ventilation hole in the upper region thereof and one cover assigned to the inner ventilation hole, which cover surrounds at least the upper end region of the measuring tube and itself has at least one outer ventilation hole, wherein at least one screen is present in the cover and which is upwardly in contact with the cover (8), wherein the screen which is upwardly adjacent to the cover extends horizontally from the measuring tube as far as a side wall of the cover, and at least four screens are provided between the one or more inner ventilation hole(s) and the one or more outer ventilation holes, so that when the device is operating at least two air bubbles are trapped in the area of the screens.
2. The Device according to claim 1, wherein two functional ventilation paths with at least two screens are provided between the inner ventilation hole and the outer ventilation hole.
3. The Device according to claim 1, wherein the notional extensions of the screens intersect each other at an angle of 90.
4. The Device according to claim 1, wherein the height of the screens is smaller than twice the height of the outer ventilation hole.
5. The Device according to claim 1, wherein the cover extends over more than 80% of the height of the measuring tube.
6. The Device according to claim 1, wherein the cross-section of the cover is constricted in the contact area between the screen and the side wall of the cover, wherein a widened area is present between two contact areas.
7. The Device according to claim 1, wherein the screens are in the form of vanes which are constructed integrally with the measuring tube.
8. The Device according to claim 1, wherein the screen forms an accommodation space for oil foam which enters through the outer ventilation hole between the measuring tube and the screen encircling the measuring tube to more than 50% of the height of the measuring tube.
9. The Device according claim 8, wherein the accommodation space has a bottom drain through an opening in a horizontal wall.
10. The Internal combustion engine, particularly for a motor vehicle with an oil-lubricated engine, wherein the oil-lubricated engine is equipped with a device according to claim 1 for measuring the fill levels of the engine oil.
Description
[0014] In the following, the invention will be explained with further reference to an exemplary embodiment represented in the drawing. In detail, the schematic diagrams show in:
[0015] FIG. 1 a diagrammatic cross-section of the device according to the invention;
[0016] FIG. 2 a diagrammatic cross-sectional view along line II-II in FIG. 1;
[0017] FIG. 3 a perspective top view of a device shown in detail along line II-II in FIG. 1;
[0018] FIG. 4 a view similar to that of FIG. 2 in a first alternative embodiment; and
[0019] FIG. 5 a view similar to that of FIG. 2 in a second alternative embodiment.
[0020] In FIG. 1, a cross-sectional view of a device 1 according to the invention is represented. Essentially, it includes a damping cup 2 with a measuring tube 4 arranged centrally therein. An ultrasonic sensor 3 is arranged below the measuring tube 4 and emits ultrasonic waves which are radiated upwards inside the measuring tube 4, are reflected on a boundary surface between a liquid, particularly oil, and air and are then received again by the ultrasonic sensor 3. The height of the fill level may then be calculated from the travel time of the signal. In general, device 1 serves in the first place to provide a measurable surface that has little foam and is calmer than the rest of the fill level in the container. For this purpose, damping cup 1 has an inlet opening 6 in the lower region thereof, through which oil from outside enters the damping cup 1 and is first degassed in an antechamber 5. Further geometrical structures are often disposed the in antechamber 5 as well, and are designed to prolong the time for which the liquid remains in the antechamber 5, but which are not represented her. The liquid passes out of antechamber 5 through an antechamber opening 15 and then enters the measuring tube 4 in degassed form and almost completely without bubbles. The level of the liquid in the measuring tube 4 is substantially equal to the level of the oil outside the damping cup 1. This is also assured particularly by an inner ventilation hole 9 at the top end of the measuring tube 4. In order to protect the measuring tube 4 from the oil foam entering through the inner ventilation hole 9, a cover 8 is provided which covers the inner ventilation hole 9 and on the other hand itself has an outer ventilation hole 10, which is offset with respect to the inner ventilation hole 9. In this case, the cover 8 is not only in the form of a small cap, as is often used otherwise, but it extends over more than 50% of the height of the damping cup, in this case even over more than 80% of the height of the damping cup, and extends as far as the region of the antechamber 5. Consequently, a very large accommodation space is created between the measuring tube 4 and the cover 8, into which oil foam entering through the outer ventilation hole 10 may be diverted and retained temporarily. This intrusive oil foam is denoted with reference number 14. The cover has a horizontal wall 12, which in this case is identical to the upper wall of the antechamber 5. Here, an additional accommodation space is defined. The oil foam 14 can then pass into the antechamber 5 through an opening 13 in said horizontal wall 12 and there is it able to drain to the outside again through the inlet opening 6. Screens 11 are arranged in the upper end region of the cover 8 and particularly in contact with the top 16 of the cover 8, which screens extend downwards from the top 16 and here also according to the invention extend from the measuring tube 4 as far as a side wall 17 of the cover 8. In the representation of FIG. 1 the visual impression given is that the screen 11 does not reach as far as the side wall 17, but this is due to the fact that the screen 11 is angled backwards here and in cross section is in contact with the annular side wall 17 of the cover 8.
[0021] FIG. 2 shows a top view of the device 1 according to FIG. 1 along line II-II. In this case, then, a cross section directly below the top 16 of the cover 8 is represented. In the top view, the measuring tube 4 and the cover 8, particularly the side wall 17 of cover 8 is visible. This cross-sectional view of the measuring tube 4 shows the inner ventilation hole 9 thereof. The outer ventilation hole 10 in the cover 8 is also visible here. Four screens 11 in the form of relatively narrow vanes emanating from the measuring tube 4 are provided here, and are constructed so as to touch the measuring tube, in particular they are integral with the measuring tube 4 and extend from the measuring tube 4 as far as side the wall 17 of the cover 8. The ventilation path of the measuring tube 4 is directed starting from the inner ventilation hole 9 in either direction around the measuring tube 4 as far as the outer ventilation hole 10. Screens 11 extend upwards as far as the top 16 of the cover 8, thus creating regions 18 that are closed at the top and to some degree laterally between the vane-like screens 11, in which air bubbles are trapped and form a barrier against the oil foam 14 entering through the outer ventilation hole 10. Instead, the oil foam 14 which enters there is able to sink in region 20 into the relatively large accommodation space between the cover 8 and the measuring tube 4. In the embodiment shown here, a third air bubble is trapped in region 19, that is to say between the two screens 11 in the region of inner ventilation hole 9. In this way, effective protection is assured.
[0022] FIG. 3 shows a perspective view of an upper end region of the damping cup 1, which is substantially the same as the embodiment of FIG. 2, but is shown in a perspective view here to illustrate the height of the screens 11, and here also a more detailed geometrical representation of the shape of the cover 8 is shown. Otherwise, identical elements are denoted with the same reference figures. It is further shown here that the height of the vane-like screens 11 is relatively small, specifically they are only slightly higher than the depth of the outer ventilation hole 10. In particular, the height of the screen 11 is less than twice the depth of the outer ventilation hole 10. In addition, the outer annular shape of cover 8 is not circular, but rather has constrictions 21 in the vicinity of the touching screens 11, so that the distance between the measuring tube 4 and the side wall 17 of the cover 8 is smallest in the area of the screens 11, and the distance between the measuring tube 4 and the side wall 17 of the cover 8 is greatest halfway between the two screens 11. As a result, the regions 18, 19 and 20 are widened and enlarged between the screen 11, so that air bubbles can form particularly readily here and a particularly good throughflow or a particularly good draining function of the entering oil foam is assured in the region 20.
[0023] The representation of FIG. 4 is similar to that of FIG. 2, but in this case the embodiment shown is slightly different. Here, two inner ventilation holes 7 are provided opposite each other in the upper rim area of the measuring tube 4. Two outer ventilation holes 10 are provided, each offset by 90 relative to said the ventilation holes. Thus, a total of four different ventilation paths are created here, which run from each of the inner ventilation holes 7 to each of the two outer ventilation holes 10. Air bubbles are trapped or may be trapped in each of the regions 19 between the two screens 11 in the area of the inner ventilation hole 7. They protect the measuring tube 4 against any oil foam 14 that might enter.
[0024] Another alternative embodiment is represented in FIG. 5, wherein the representation again corresponds to the views of FIGS. 2 and 4. Here too, two inner ventilation holes 7 and two outer ventilation holes 10 are present, thus resembling the embodiment of FIG. 4. In this case however, two screens 11 are provided between the inner ventilation holes 7 and the outer ventilation holes 10 in each ventilation path. Accordingly, a total of eight screens 11 are provided, and a total of four regions 18 are formed between each two screens 11, in each of which an air bubble is trapped. One air bubble is also trapped in each of the two regions 19 adjacent to inner ventilation hole 7. There are no air bubbles trapped in each of the regions 20, because these are the regions where the air escapes through outer ventilation hole 10.
[0025] All of the features explained in the preceding description and in the claims can be combined in any permutation with the features of the independent claim. The disclosure of the invention is thus not limited to the combinations of features that have been described and claimed, but all feature combinations that are practicable within the scope of the invention are rather to be treated as having been disclosed.
